1. Field of the Invention
The present invention relates to a barrel mounted to image-taking apparatus such as silver halide camera and digital still cameras, and more specifically video cameras, etc.
2. Description of the Related Art
FIG. 6 shows a barrel of a conventional camera (see Japanese Patent Application Laid-Open Publication No. H07(1995)-043584). In the figure, numeral 101 denotes a rectilinear barrel, and this rectilinear barrel 101 is positioned inside a differential barrel not illustrated. When this differential barrel moves in the optical axis direction while the differential barrel rotates around the optical axis, the rectilinear barrel 101 moves in the optical axis direction in linkage with the movement of the differential barrel while the rectilinear barrel 101 does not rotate around the optical axis.
To the rectilinear barrel 101, three guide groove portions 101d extending along the optical axis direction are located at nearly even intervals. To guide the groove portion 101d, a cam pin (not illustrated) mounted to a lens holding member to be assembled inside the rectilinear barrel 101 is engaged.
At the rear end portion of the rectilinear barrel 101, a flange portion 101a that extends along the circumferential direction of the rectilinear barrel 101 is positioned. At the position of the phase same as that of the guide groove portion 101d of the flange portion 101a, an opening 101c for passing the cam pin is provided. When a lens holding member is assembled to the rectilinear barrel 101, the cam pin can be guided to guide the groove portion 101d in such a manner as to pass the opening portion 101c from the rear side of the rectilinear barrel 101.
In addition, to the flange portion 101a, a protruded portion 101b is positioned at the location of the phase same as that of the opening portion 101c. This protruded portion 101b prevents the rectilinear barrel 101 from rotating around the optical-axis by engaging with a rectilinear groove portion formed in a fixed barrel (either not illustrated).
As described above, in the conventional lens barrel, the opening portion 101c and the protruded portion 101b are arranged at the position of the same phase. This is because strength is weakened at the place where the opening portion 101c of the flange portion 101a is formed because the size in the height direction of the flange portion is shortened. That is, the protruded portion 101b is arranged at the position of the phase same as that of the opening portion 101 and the strength of the flange portion 101a is prevented from being degraded.
However, if it is mandatory to arrange the protruded portion 101b at the position of the phase same as that of opening portion 101c, the degree of design freedom is impaired. That is, the protruded portion 101b must be arranged in such a manner as to engage with the rectilinear groove portion formed in the fixed barrel. Consequently, the opening portion 101c, the guide groove portion 101d, the protruded portion 101b, and the rectilinear groove portion of the fixed barrel must be arranged at the position of the same phase. This may impair the degree of design freedom.
It is an object of the present invention to provide a lens apparatus which is easy to assemble and at the same time which achieves a high degree of design freedom while securing sufficient strength at the flange portion.
The lens apparatus which is one aspect of the present invention comprises a first, a second, and a third barrel members. The first barrel member comprises a guide portion which is guided in an optical axis direction and a cam follower portion provided on the guide portion. The second barrel member has a first groove portion which guides the guide portion formed on the circumferential wall in the optical axis direction, and at the optical axis direction end of the circumferential wall, a flange portion is formed. In the third barrel member, there formed is a cam portion which engages with the cam follower portion and drives the first barrel member in the optical axis direction. In addition, the lens apparatus has a drive mechanism which rotates and drives the third barrel member around the optical axis.
And on the periphery of the flange portion, a concave portion which evacuates to the drive mechanism is formed, and in the inner circumference of the flange portion, an opening portion is formed for allowing the cam follower portion to pass when the guide portion is engaged with the first groove portion. Furthermore, in the second barrel member, the first groove portion and the opening portion are formed in different positions in the circumferential direction and at the same time, on the circumferential wall, the second groove portion is formed to assemble the guide portion into the first groove portion from the position of the opening portion.
The features of the lens apparatus and image-taking apparatus according to the present invention will become more apparent from the following description taken in connection with the accompanying drawings.